From: Eric Dumazet <erdnetdev@xxxxxxxxx> Date: Thu, 10 Jun 2021 20:20:11 +0200 > On 5/21/21 8:20 PM, Kuniyuki Iwashima wrote: > > When we call close() or shutdown() for listening sockets, each child socket > > in the accept queue are freed at inet_csk_listen_stop(). If we can get a > > new listener by reuseport_migrate_sock() and clone the request by > > inet_reqsk_clone(), we try to add it into the new listener's accept queue > > by inet_csk_reqsk_queue_add(). If it fails, we have to call __reqsk_free() > > to call sock_put() for its listener and free the cloned request. > > > > After putting the full socket into ehash, tcp_v[46]_syn_recv_sock() sets > > NULL to ireq_opt/pktopts in struct inet_request_sock, but ipv6_opt can be > > non-NULL. So, we have to set NULL to ipv6_opt of the old request to avoid > > double free. > > > > Note that we do not update req->rsk_listener and instead clone the req to > > migrate because another path may reference the original request. If we > > protected it by RCU, we would need to add rcu_read_lock() in many places. > > > > Link: https://lore.kernel.org/netdev/20201209030903.hhow5r53l6fmozjn@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > > Suggested-by: Martin KaFai Lau <kafai@xxxxxx> > > Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxxxx> > > Acked-by: Martin KaFai Lau <kafai@xxxxxx> > > --- > > net/ipv4/inet_connection_sock.c | 71 ++++++++++++++++++++++++++++++++- > > 1 file changed, 70 insertions(+), 1 deletion(-) > > > > diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c > > index fa806e9167ec..07e97b2f3635 100644 > > --- a/net/ipv4/inet_connection_sock.c > > +++ b/net/ipv4/inet_connection_sock.c > > @@ -695,6 +695,53 @@ int inet_rtx_syn_ack(const struct sock *parent, struct request_sock *req) > > } > > EXPORT_SYMBOL(inet_rtx_syn_ack); > > > > +static struct request_sock *inet_reqsk_clone(struct request_sock *req, > > + struct sock *sk) > > +{ > > + struct sock *req_sk, *nreq_sk; > > + struct request_sock *nreq; > > + > > + nreq = kmem_cache_alloc(req->rsk_ops->slab, GFP_ATOMIC | __GFP_NOWARN); > > + if (!nreq) { > > + /* paired with refcount_inc_not_zero() in reuseport_migrate_sock() */ > > + sock_put(sk); > > + return NULL; > > + } > > + > > + req_sk = req_to_sk(req); > > + nreq_sk = req_to_sk(nreq); > > + > > + memcpy(nreq_sk, req_sk, > > + offsetof(struct sock, sk_dontcopy_begin)); > > + memcpy(&nreq_sk->sk_dontcopy_end, &req_sk->sk_dontcopy_end, > > + req->rsk_ops->obj_size - offsetof(struct sock, sk_dontcopy_end)); > > + > > + sk_node_init(&nreq_sk->sk_node); > > + nreq_sk->sk_tx_queue_mapping = req_sk->sk_tx_queue_mapping; > > +#ifdef CONFIG_XPS > > + nreq_sk->sk_rx_queue_mapping = req_sk->sk_rx_queue_mapping; > > +#endif > > + nreq_sk->sk_incoming_cpu = req_sk->sk_incoming_cpu; > > + refcount_set(&nreq_sk->sk_refcnt, 0); > > Not sure why you clear sk_refcnt here (it is set to 1 later) I thought it was safer, but I'm fine to remove the line. > > > + > > + nreq->rsk_listener = sk; > > + > > + /* We need not acquire fastopenq->lock > > + * because the child socket is locked in inet_csk_listen_stop(). > > + */ > > + if (sk->sk_protocol == IPPROTO_TCP && tcp_rsk(nreq)->tfo_listener) > > + rcu_assign_pointer(tcp_sk(nreq->sk)->fastopen_rsk, nreq); > > + > > + return nreq; > > +} > > Ouch, this is going to be hard to maintain... How could I make it less hard ... ? > > > > > > + > > +static void reqsk_migrate_reset(struct request_sock *req) > > +{ > > +#if IS_ENABLED(CONFIG_IPV6) > > + inet_rsk(req)->ipv6_opt = NULL; > > +#endif > > +} > > + > > /* return true if req was found in the ehash table */ > > static bool reqsk_queue_unlink(struct request_sock *req) > > { > > @@ -1036,14 +1083,36 @@ void inet_csk_listen_stop(struct sock *sk) > > * of the variants now. --ANK > > */ > > while ((req = reqsk_queue_remove(queue, sk)) != NULL) { > > - struct sock *child = req->sk; > > + struct sock *child = req->sk, *nsk; > > + struct request_sock *nreq; > > > > local_bh_disable(); > > bh_lock_sock(child); > > WARN_ON(sock_owned_by_user(child)); > > sock_hold(child); > > > > + nsk = reuseport_migrate_sock(sk, child, NULL); > > + if (nsk) { > > + nreq = inet_reqsk_clone(req, nsk); > > + if (nreq) { > > + refcount_set(&nreq->rsk_refcnt, 1); > > + > > + if (inet_csk_reqsk_queue_add(nsk, nreq, child)) { > > + reqsk_migrate_reset(req); > > + } else { > > + reqsk_migrate_reset(nreq); > > + __reqsk_free(nreq); > > + } > > + > > + /* inet_csk_reqsk_queue_add() has already > > + * called inet_child_forget() on failure case. > > + */ > > + goto skip_child_forget; > > + } > > + } > > + > > inet_child_forget(sk, req, child); > > +skip_child_forget: > > reqsk_put(req); > > bh_unlock_sock(child); > > local_bh_enable(); > >
